1. Field of the Invention
The present invention relates to an optical recording medium and a method of producing such a medium.
2. Statement of the Prior Art
As mass information recording media, the importance of optical recording media, such as optical recording discs has gradually increased, recently. Among the optical recording media, there are an erasable type of optical recording medium such as a phase change type or an magneto-optical type of optical recording medium and a write-once type of optical recording medium such as a pit formation type of optical recording medium.
In recent years, there have been proposed optical recording media that enable additional writing or recording in conformity with the compact disc (hereinafter CD for short) standards. For instance, see "Nikkei Electronics", No. 465, page 107 (Jan. 23, 1989), and "SPIE", Vol. 1078, Optical Data Storage Topical Meeting, 80 (1989), held at the Osaka Science & Technology Center on Mar. 3, 1989 by the corporation, Kinki Chemical Association, the section of functional dyes. These optical recording discs each include on a transparent resin substrate a dye layer, an Au reflecting layer and a protecting layer, which are laminated thereon in this order. More specifically, the reflective layer is directly in contact with the dye layer.
Because of using an organic dye, however, this optical recording disc shows material degradation under severe weather conditions, especially under ultraviolet rays in the solar light and so on. This is a special disadvantage for information storing mediums which have to maintain high reliability for a long time after recording.
Under the situations mentioned above, the inventors have come up with optical recording media each including a recording thin film using an inorganic compound that decomposes by laser heating and releases gases, more specifically, silver oxide or iron nitride instead of organic dyes (Japanese Patent Application Nos. 3-119474 and 3-221025).
These optical recording media show high resistance to light and high reliability, as compared with media using dyes. However, a problem with these media is that, when they are stored over an extended period under severe conditions of high temperature, high humidity, etc., there are increases in cross talks and jitters.
An object of the invention is therefore to provide an optical recording medium including a recording thin film having high reliability to light and using an inorganic compound, which has a reflectivity of more than 70% in connection with a dielectric layer and a reflector. This disc is fully compatible to present CDS when reproduced.